The objective of the proposed study is to investigate the differences between beta 1 and beta 2 adrenoceptors. The accumulated knowledge suggests that beta 1-adrenoceptor (myocardial) and beta 2-adrenoceptor (bronchial) are structurally distinct entitities. Synthesis of a series of new 1-(4'-substitute aryloxy)-3-alkyl-propan-2-ols as potential beta 1-adrenoceptor antagonists and the characterization of their beta 1 vs. beta 2 selectivity as compared to known beta 1-antagonists should elucidate the properties leading to such selectivity. The selectivity of the antagonists will be determined by in vitro competition studies using both isolated receptor systems and isolated perfused organs. The primary benefits of this study are: better understanding of the differences between beta 1 and beta 2-adrenoceptors and increased knowledge of structure-activity relationship (SAR) of beta-adrenoceptor antagonists.